I'm afraid I can't give a direct answer on the number of data points, in part because the information we collect through your web browsing isn't used to identify specific data points about you, as an individual. It's used to create generic profiles about our users that could be then used for providing services and providing advertising. So there may be x number of data points that simply result in a conclusion that you like American-made cars. There's no specific line that way.
In terms of how long we retain that sort of information, if we're dealing with the web search history, there's a tool called Ads Preferences Manager, on which you can go in and take a look at the buckets we've identified as applying to your particular interests, and then correct them or delete them. You can either make the point to us that, as the example was made, someone is a hunter—that you're either a very specific kind of hunter or that you're not at all.
For example, from some of my search habits, sometimes Google thinks that I'm a 35-year-old woman. I don't know quite how it arrives at that conclusion, but I have to go in and correct it. It's a click on an X, and then that data point is erased and it's reconstructed, hopefully appropriately.